XWnt-5A, a member of the nontransforming Wnt-5A class of Wnt ligands, is required for convergent extension movements in Xenopus embryos. XWnt-5A knockdown phenocopies paraxial protocadherin (XPAPC) loss of function: involuted mesodermal cells fail to align mediolaterally, which results in aberrant movements and a selective inhibition of constriction. XWnt-5A depletion was rescued by coinjection of XPAPC RNA, indicating that XWnt-5A acts upstream of XPAPC. XWnt-5A, but not XWnt-11, stimulates XPAPC expression independent of the canonical Wnt/beta-catenin pathway. We show that transcriptional regulation of XPAPC by XWnt-5A requires the receptor tyrosine kinase Ror2. XWnt-5A/Xror2 signal through PI3 kinase and cdc42 to activate the JNK signaling cascade with the transcription factors ATF2 and c-jun. The Wnt-5A/Ror2 pathway represents an alternative, distinct branch of noncanonical Wnt signaling that controls gene expression and is required in the regulation of convergent extension movements in Xenopus gastrulation.

Wnt binding to members of the seven-span transmembrane Frizzled (Fz) receptor family controls essential cell fate decisions and tissue polarity during development and in adulthood. The Fzmediated membrane recruitment of the cytoplasmic effector Dishevelled (Dvl) is a critical step in Wnt/β-catenin signaling initiation, but how Fz and Dvl act together to drive downstream signaling events remains largely undefined. Here, we use an Fz peptide-based microarray to uncover a mechanistically important role of the bipartite Dvl DEP domain and C terminal region (DEP-C) in binding a three-segmented discontinuous motif in Fz. We show that cooperative use of two conserved motifs in the third intracellular loop and the classic C-terminal motif of Fz is required for DEP-C binding and Wnt-induced β-catenin activation in cultured cells and Xenopus embryos. Within the complex, the Dvl DEP domain mainly binds the Fz C-terminal tail, whereas a short region at the Dvl C-terminal end is required to bind the Fz third loop and stabilize the Fz-Dvl interaction. We conclude that Dvl DEP-C binding to Fz is a key event in Wnt-mediated signaling relay to β-catenin. The discontinuous nature of the Fz-Dvl interface may allow for precise regulation of the interaction in the control of Wnt-dependent cellular responses.peptide microarray | protein-protein interaction | Wingless signaling

Much of the biological functions of a cell are dictated by the intricate motion of proteins within its membrane over a spatial range of nanometers to tens of micrometers and time intervals of microseconds to minutes. While this rich parameter space is not accessible to fluorescence microscopy, it can be within reach of interferometric scattering (iSCAT) particle tracking. Being sensitive even to single unlabeled proteins, however, iSCAT is easily accompanied by a large speckle-like background, which poses a substantial challenge for its application to cellular imaging. Here, we show that these difficulties can be overcome and demonstrate tracking of transmembrane epidermal growth factor receptors (EGFR) with nanometer precision in all three dimensions at up to microsecond speeds and tens of minutes duration. We provide unprecedented examples of nanoscale motion and confinement in ubiquitous processes such as diffusion in the plasma membrane, transport on filopodia, and endocytosis..

Convergent extension movements occur ubiquitously in animal development. This special type of cell movement is controlled by the Wnt/planar cell polarity (PCP) pathway. Here we show that Xenopus paraxial protocadherin (XPAPC) functionally interacts with the Wnt/PCP pathway in the control of convergence and extension (CE) movements in Xenopus laevis. XPAPC functions as a signalling molecule that coordinates cell polarity of the involuting mesoderm in mediolateral orientation and thus selectively promotes convergence in CE movements. XPAPC signals through the small GTPases Rho A and Rac 1 and c-jun N-terminal kinase (JNK). Loss of XPAPC function blocks Rho A-mediated JNK activation. Despite common downstream components, XPAPC and Wnt/PCP signalling are not redundant, and the activity of both, XPAPC and PCP signalling, is required to coordinate CE movements

The Wnt/␤-catenin signaling pathway is crucial for proper embryonic development and tissue homeostasis. The phosphoprotein dishevelled (Dvl) is an integral part of Wnt signaling and has recently been shown to interact with the multifunctional scaffolding protein ␤-arrestin. Using Dvl deletion constructs, we found that ␤-arrestin binds a region N-terminal of the PDZ domain of Dvl, which contains casein kinase 1 (CK1) phosphorylation sites. Inhibition of Wnt signaling by CK1 inhibitors reduced the binding of ␤-arrestin to Dvl. Moreover, mouse embryonic fibroblasts lacking ␤-arrestins were able to phosphorylate LRP6 in response to Wnt-3a but decreased the activation of Dvl and blocked ␤-catenin signaling. In addition, we found that ␤-arrestin can bind axin and forms a trimeric complex with axin and Dvl.